Correct oil
03-29-2014, 10:46 PM
#22
No, I'm not forgetting that. The concepts which you clearly have limited understanding of, but are hinting at, are related to boundary lubrication, which is also covered in one of the links that I provided you. I would suggest less typing and more reading. Start with looking up what a centrifuge is, unless you just want to talk about purifiers and clarifiers instead of tribology.
Btw, I'm not discounting what you say about oil pressure's importance. It certainly is, but there is much more to it.
Btw, I'm not discounting what you say about oil pressure's importance. It certainly is, but there is much more to it.
03-31-2014, 11:12 AM
#23
You have provided links to formulas engine builders use to give a starting point for what oil to use. At the end of the day, you have two options for understanding how your engine is handling the oil. Pressure, and oil analysis. We can all plug numbers into formulas. If we have no way of verifying our calculations though, it doesn't do us much good. Much of the time academia doesn't replace real world values. Data can reinforce theory though. Since my engineering degree doesn't start with mechanical, I apologize for mistakenly using centrifuge instead of centrifugal motion. Maybe you could apply the links you copied and pasted to allude to what oil might be recommended per bearing clearance?
The point of the links I provided in a hasty google search were just to give an idea of how manufacturers arrive at a recommended oil weight, and to hopefully show why these internet myths about "rule of thumb" and how to figure out what weight oil to use are bs. How much oil pressure do you need to supply a journal bearing in theory? 1psig, Bob
It's all about keeping the supply of oil adequate, because the hydrodynamic wedge creates its own pressure with a peak pressure at the thinnest point of the wedge. In reality, you need that pressure to supply all the parts of the engine with lube oil, which blownbluez06 did a great job of explaining why. As to figure out what oil to use, I just ask the manufacturer. They've actually done the crazy math to figure out what oil to recommend, and in the case of MAN or Wartsila for huge 30,000 hp ship engines it's probably just Shell Rotella. Nothing special- just 1,000 gallons of it changed regularly based on oil lab analysis.The simple answer is that you need a thicker oil, OP
The bearings are arguably the most important thing to lube in your engine.
04-19-2014, 09:27 AM
#24
Melting Slicks
Oil pressure, just like boost is a measurement based on of the resistance to forward flow. The key to selecting proper viscosity oil is to select it based on things like internal clearances, load, type of use and temperature range of use.
If you have tight clearances, you need thinner oil. Looser bearing clearances need thicker oil. This is in an attempt to maintain what Joe Gibbs calls the "Hydrodynamic Oil Wedge" or protective boundary layer of oil.
Here's a video you can watch that may help.
If you have tight clearances, you need thinner oil. Looser bearing clearances need thicker oil. This is in an attempt to maintain what Joe Gibbs calls the "Hydrodynamic Oil Wedge" or protective boundary layer of oil.
Here's a video you can watch that may help.
bringing this back up, its time for my second oil change for my car and im not so sure im happy with the first choice i was recommended.
how would one figure out what is good if they do not have the info from the builder?
can they use info from past oil used to determine what is needed?
the oil i run now is straight 40w vr1, im just worried on cold starts. it seems to screw with my oil pressure when its cold vs warm and im not so sure im happy with it. since i started using it ive always waited till the car was fully warm before driving it.
i like the vr1 brand with the added zinc etc but they don't make anything like a 5 40 or 10 40.\
motor is a forged ls2, stock cubes, arun cam, stock modded rockers
pressure with the straight 40 wt
idle 33psi when hot 40ish cold
50psi cruising hot 60ish cold
whats odd tho is if i start cruising and the oil isn't up to temp it will be around 45psi then after a few miles it will jump to around 60psi then when fully warm creep down to 50psi and remain there until i shutdown.
not sure on wot, haven't done much of it with the new setup...
motor has around 1500 miles on it id say, no noises and runs great, doesn't make noise with the straight 40w on cold starts either...
Last edited by StealthFRC; 04-19-2014 at 09:31 AM.